Photodynamic therapy for experimental tumors using ATX-S10(Na), a hydrophilic chlorin photosensitizer, and diode laser

ATX-S10(Na), a hydrophilic chlorin photosensitizer having an absorption max imum at 670 nm, is a candidate second-generation photosensitizer for use in photodynamic therapy (PDT) for cancer treatment, The effectiveness of PDT using ATX-S10(Na) and a diode laser for experimental tumors was evaluated i n vitro and in vivo, In-vitro PDT using ATS-S10(Na) and the diode laser sho wed drug concentration-, laser dose- and drug exposure time-dependent cytot oxicity to various human and mouse tumor cell lines. In Meth-A sarcoma-impl anted mice, optimal PDT conditions were found where tumors were completely eliminated without any toxicity. Against human tumor xenografts in nude mic e, the combined use of 5 mg/kg ATX-S10(Na) and 200 J/cm(2) laser irradiatio n 3 h after ATX-S10(Na) administration showed excellent anti-tumor activity , and its efficacy was almost the same as that of PDT using 20 mg/kg porfim er sodium and a 100 J/cm(2) excimer dye laser 48 h after porfimer sodium in jection, Microscopic observation of tumor tissues revealed that PDT using A TX-S10(Na) and the diode laser induced congestion, thrombus and degeneratio n of endothelial cells in tumor vessels, indicating that a vascular shutdow n effect plays an important role in the anti-tumor activity of PDT using AT X-S10(Na) and the diode laser.